使用Mongo C#Driver序列化不可变值类型

Question

我有许多不可变的值类型类,例如EmailAddress,它确保任何非null实例有效.我希望"123@abc.com"在使用MongoDB C#Driver持久化时,将这些类型的对象的序列化控制为标准字符串表示().

我尝试过实现IBsonSerilizer它,但它只允许根级别的对象或数组.我能够用Json.NET实现适当的Json Serilization,我应该采用不同的方法吗？

Answer 1

我假设你的意思是这样的EmailAddress类:

[BsonSerializer(typeof(EmailAddressSerializer))]
public class EmailAddress
{
    private string _value;

    public EmailAddress(string value)
    {
        _value = value;
    }

    public string Value
    {
        get { return _value; }
    }
}

我使用了一个属性将EmailAddress类链接到自定义序列化程序,可以像这样实现:

public class EmailAddressSerializer : BsonBaseSerializer
{
    public override object Deserialize(BsonReader bsonReader, Type nominalType, Type actualType, IBsonSerializationOptions options)
    {
        if (bsonReader.GetCurrentBsonType() == BsonType.Null)
        {
            bsonReader.ReadNull();
            return null;
        }
        else
        {
            var value = bsonReader.ReadString();
            return new EmailAddress(value);
        }
    }

    public override void Serialize(BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
    {
        if (value == null)
        {
            bsonWriter.WriteNull();
        }
        else
        {
            var emailAddress = (EmailAddress)value;
            bsonWriter.WriteString(emailAddress.Value);
        }
    }
}

您不能将EmailAddress序列化为根文档(因为它不是文档...).但您可以使用嵌入在其他文档中的EmailAddress.例如:

public class Person
{
    public int Id { get; set; }
    public EmailAddress EmailAddress { get; set; }
}

您可以使用以下代码进行测试:

var person = new Person { Id = 1, EmailAddress = new EmailAddress("joe@xyz.com") };
var json = person.ToJson();
var rehyrdated = BsonSerializer.Deserialize<Person>(json);

生成的JSON/BSON文档是:

{ "_id" : 1, "EmailAddress" : "joe@xyz.com" }